Automated hydroponic greenhouse factory

ABSTRACT

Plants are grown by using a nutrient film over a trough of nutrient solution. The film is opaque and includes apertures for holding plants. The film is rolled out for growing the pants and rolled up for plant harvesting.

CROSS REFERENCES TO RELATED APPLICATIONS

This patent application is a Continuation patent application of commonlyowned U.S. patent application Ser. No. 15/817,349, entitled: AUTOMATEDHYDROPONIC GREENHOUSE FACTORY, filed on Nov. 20, 2017, which is aContinuation patent application of commonly owned U.S. patentapplication Ser. No. 14/414,121, entitled: AUTOMATED HYDROPONICGREENHOUSE FACTORY, filed on Jul. 1, 2013, now U.S. Pat. No. 9,848,544,which is a § 371 of commonly owned PCT Application PCT/IB2013/055378,entitled: AUTOMATED HYDROPONIC GREENHOUSE FACTORY, filed Jul. 1, 2013 (§371 date of Jan. 12, 2015), which claims priority from commonly ownedU.S. Provisional Patent Application No. 61/670,147, filed Jul. 11, 2012,now abandoned, all of the aforementioned patent applicationsincorporated by reference in their entirety herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to hydroponics and, more particularly, toinnovative automated hydroponic systems and methods for raisingcommercially valuable plants.

Traditionally, fruit and vegetables have been grown where and when theclimate allows. In recent decades massive quantities of produce havebeen shipped, thousands of miles, from the growing areas to theconsumers' concentrations. The rising prices of energy and water havemade fresh produce prices go up continuously due to the growing cost oftransportation and the lack of water in the growing areas. It is forthese reasons, among others, that there is a growing demand for localproduction. To satisfy this growing demand for local production ofvegetables, protected crops technology and techniques and greenhouseenclosures are needed. Growing crops indoors in order to protect themfrom the ambient conditions that are not suitable for their growth isvery expensive. Both the amortization of the building, and the runningcost of maintaining the suitable conditions inside, are costs that arerelative to the area of the building. Hydroponics is a preferred methodof growing indoors because it is a cost effective growing method. Addingautomation to hydroponics creates an optimal solution for high yieldsper area.

SUMMARY OF THE INVENTION

The fast growth of plants when grown in systems of the present inventionaccording to methods of the present invention, combined with thereduction of walkway area provided by the present invention, combinedwith spacing of the plants as they grow, as provided by the presentinvention, gives maximum yields per building area thus making thebuilding in which the plants are grown cost efficient.

According to the present invention there is provided an apparatus forgrowing plants, including: (a) a pool for a nutrient solution; (b) asufficient number of substantially identical trays, for at least partialimmersion in the nutrient solution, to be arranged in a plurality ofrows within the pool such that each row includes at least one the trayand also includes a gap wide enough to receive one and only one of thetrays from an adjacent the row, each tray being adapted to hold at leastone of the plants so that roots of the at least one plant are at leastpartly immersed in the nutrient solution; (c) for each row, a mechanismfor moving the at least one tray of the each row within the each row,thereby changing a location of the gap within the row relative to the atleast one tray of the row; and (d) a mechanism for moving one of the atleast one tray of each row into the gap of an adjacent the row.

According to the present invention there is provided a method of growingplants, including the steps of: (a) arranging, in a pool of a nutrientsolution, a sufficient number of substantially identical trays to bearranged in three rows within the pool such that each row includes aplurality of the trays and also includes a gap wide enough to receiveone and only one of the trays from an adjacent the row, each tray beingadapted to hold at least one of the plants so that roots of the at leastone plant are at least partly immersed in the nutrient solution; (b)planting at least one of the plants in each of the trays of only one ofthe rows, leaving the trays of the other rows as empty trays, therebytransforming the trays of the only one row into planted trays; and (c)exchanging the trays among the rows, only within the pool, so that theplanted trays are located only in the other rows, with every tray thatis adjacent to a planted tray being one of the empty trays.

According to the present invention there is provided a tray, forsupporting at least one plant with roots thereof at least partlyimmersed in a nutrient solution, including a substantiallyparallelepipedal block having, for each plant, an aperture that extendsfrom a top side of the tray to a bottom side of the tray, and having, oneach long side thereof, at least one protrusion for preventing adhesionof the tray to an adjacent tray when the tray and the adjacent tray areat least partly immersed in the nutrient solution.

According to the present invention there is provided a method of growinga plant, including the steps of (a) suspending the plant so that rootsof the plant are at least partly immersed in a nutrient solution havinga depth of between about 4 centimeters and about 20 centimeters; and (b)causing the nutrient solution to flow past the roots.

According to the present invention there is provided a method of growinga plant, including the steps of: (a) suspending the plant so that theroots of the plant are at least partly immersed in a nutrient solution;and (b) using airlift pumping to cause the nutrient solution to flowpast the roots.

According to the present invention there is provided a device forgrowing a plant, including: (a) a mechanism for suspending the plant sothat the roots of the plant are at least partly immersed in a nutrientsolution; and (b) an airlift pump for causing the nutrient solution toflow past the roots.

According to the present invention there is provided a method of growinga plant, including the steps of: (a) suspending the plant so that theroots of the plant are at least partly immersed in a nutrient solution;and (b) maintaining a concentration of dissolved oxygen in the nutrientsolution at least about 80% of saturation.

According to the present invention there is provided a device forgrowing a plant, including: (a) a mechanism for suspending the plant sothat the roots of the plant are at least partly immersed in a nutrientsolution; and (b) a mechanism for maintaining a concentration ofdissolved oxygen in the nutrient solution at at least about 80% ofsaturation.

According to the present invention there is provided a system forgrowing plants including: (a) a plurality of hydroponic units; and (b) asingle manifold for sampling a respective nutrient solution of eachunit, thereby providing a sample of the respective nutrient solution;and (c) a controller for: (i) measuring at least one property of eachsample, and (ii) in response to the measuring, and via the manifold,adjusting the respective nutrient solution of which the each sample is asample.

According to the present invention there is provided a device forproviding adjustable shade, including: (a) a plurality of parallellinear support members; (b) substantially enclosing each support member:a flexible tube; and (c) an inflation mechanism for reversibly inflatingeach tube.

According to the present invention there is provided a system forgrowing and harvesting plants, including: (a) a bed, for growing theplants, that includes a mechanism for moving the plants to a side of thebed when the plants are ready for harvesting; and (b) a harvester,adapted to be positioned adjacent to the side of the bed, for harvestingthe plants as the plants are moved by the mechanism to the side of thebed.

According to the present invention there is provided a method of growingand harvesting plants, including: (a) placing the plants in a bedwherein the plants grow until ready to be harvested; and (b) moving theplants within the bed to a side of the bed while using a mechanicalharvester at the side of the bed to harvest the plants.

According to the present invention there is provided a system forgrowing a plurality of plants, including: (a) a plurality ofsubstantially parallel troughs for supporting a nutrient solution; (b)an opaque flexible sheet having a plurality of apertures therein forsupporting the plants; and (c) a roller for reversibly unrolling theflexible sheet parallel to the troughs and positioned relative to thetroughs so that when the flexible sheet is unrolled the flexible sheetsubstantially covers at least a portion of the plurality of troughs,with each aperture above a respective the trough and sufficiently closeto the trough that roots of a plant that is supported by the eachaperture are at least partly immersed in the nutrient solution.

According to the present invention there is provided a method of growinga plurality of plants, including the steps of: (a) placing a nutrientsolution in a plurality of substantially parallel troughs; (b) spreadinga flexible opaque sheet, that includes a plurality of apertures forsupporting the plants, above at least a portion of the troughs so thateach aperture is above a respective the trough; and (c) inserting eachof the plants in a respective one of the apertures so that the one plantis supported by the respective aperture with roots of the one plant atleast partly immersed in the nutrient solution.

A first aspect of the present invention is a rotating field system forgrowing plants. A basic apparatus of the first aspect includes a poolfor a nutrient system, a plurality of substantially identical trays tobe at least partially immersed in the pool, and mechanisms for movingthe trays within the pool. There are enough trays to be arranged in aplurality of rows within the pool such that each row includes at leastone tray and also includes a gap wide enough to receive exactly one trayfrom an adjacent row. Each tray is adapted to hold at least one of theplants so that the roots of the plant(s) are at least partly immersed inthe nutrient solution. For each row there is a mechanism for moving thetray(s) of the row within the row to change the location of the gapwithin the row relative to the tray(s) of the row. The apparatus alsoincludes a mechanism for moving one of the tray(s) of each row into thegap of an adjacent row.

Preferably, the apparatus includes enough trays for each row to includetwo or more trays.

Preferably, each tray is adapted to float in the nutrient solution.(Alternatively, but less preferably, the trays could be supported in thepool on wheels or rollers.)

Preferably, the mechanism for moving the trays of a row within that rowmoves the trays in only one direction within that row. Most preferably,these mechanisms are arranged to move the trays of adjacent rows inopposite directions.

Preferably, the tray that is moved from a row into the gap of anadjacent row is an end tray of the row from which the tray is moved.

Preferably, the apparatus includes at least three rows of trays,arranged so that at least one of the rows is between two other rows. Themechanism for moving trays between rows is operative to move trays ofthe at least one row to either or the two other rows.

Preferably, the apparatus also includes a harvester that is adapted tobe positioned to an end of one of the rows, for harvesting the plant(s)that is/are held by the tray at that end of the row.

In a basic method of the first aspect of the present invention,substantially identical trays are arranged in a pool of a nutrientsolution. There are enough trays to be arranged in three rows within thepool, with each row including two or more trays and a gap wide enough toreceive exactly one tray from an adjacent row. Each tray is adapted tohold one or more of the plants so that the roots of the plant(s) are atleast partly immersed in the nutrient solution. One or more of theplants is/are planted in each tray of only one of the three rows,leaving the trays of the other rows as empty trays (i.e., trays that areempty of the plants), thereby transforming the trays of that one rowinto planted trays. The trays then are exchanged among the rows, onlywithin the pool, so that the planted trays are located only in the twoother rows, with every tray that is adjacent to a planted tray being anempty tray.

Preferably, when the plants are planted in the trays of the only onerow, the plants are sufficiently small to thrive despite being plantedin adjacent trays. The trays are exchanged after the plants have grownsufficiently to require spacing apart of the adjacent trays in order forthe plants to continue to thrive.

Preferably, the exchanging of the trays is effected by steps includingmoving one of the trays of one of the rows into the gap of an adjacentrow.

Preferably, the exchanging results in the only one row being occupiedonly by empty trays. Then, one or more or the plants again are plantedin each tray of the only one row.

The trays of the first aspect of the present invention are themselvesthe second aspect of the present invention. A basic tray, for supportingone or more plants with the roots of the plant(s) at least partlyimmersed in a nutrient solution, includes a substantiallyparallelepipedal block that has two parallel long sides, two parallelshort sides, a top side and a bottom side, and that also has, for eachplant, an aperture that extends from the top side of the tray to thebottom side of the tray. Each long side of the block has one or moreprotrusions for preventing adhesion of the tray to an adjacent tray whenthe two trays are at least partly immersed in the nutrient solution.

Preferably, the block is made of a material, such as low-densitypolypropylene, whose density is such that the block floats in thenutrient solution.

Preferably, the tray includes a champfer at each lateral edge. (Thelateral edges are the edges where the long and short sides meet.) Mostpreferably, each champfer is at an angle of between about 15□ and about25□ relative to an adjacent side of the tray.

Preferably, the aperture(s) is/are arranged to support the plant(s), forexample, by the leaves of the plant(s) or by the roots of the plant(s).

A third aspect of the present invention is a method for growing a plant.According to the method, the plant is suspended so that the roots of theplant are at least partly immersed in a nutrient solution that isbetween about 4 centimeters and about 20 centimeters deep and thatpreferably includes dissolved oxygen at a saturation level of at leastabout 80%. The nutrient solution is caused to flow past the roots.

Preferably, the nutrient solution is between about 5 centimeters andabout 6 centimeters deep.

Preferably, airlift pumping is used to cause the nutrient solution toflow past the roots. Most preferably, the airlift pumping is effected ata sufficiently high flow rate to achieve at least about 80% dissolvedoxygen saturation of the nutrient solution.

A fourth aspect of the present invention is a method and device forgrowing a plant. According to the method, the plant is suspended so thatthe roots of the plant are at least partly immersed in a nutrientsolution. Airlift pumping is used to cause the nutrient solution to flowpast the roots. The device includes a mechanism for suspending the plantso that the roots of the plant are at least partly immersed in anutrient solution and an airlift pump for causing the nutrient solutionto flow past the roots.

A fifth aspect of the present invention is a method and device forgrowing a plant. According to the method, the plant is suspended so thatthe roots of the plant are at least partly immersed in a nutrientsolution. The concentration of dissolved oxygen in the nutrient solutionis maintained at at least about 80% of saturation The device includes amechanism for suspending the plant so that the roots of the plant are atleast partly immersed in a nutrient solution and a mechanism formaintaining the concentration of dissolved oxygen in the nutrientsolution at at least about 80% of saturation.

A sixth aspect of the present invention is a system for growing plants.A basic such system includes a plurality of hydroponic units, a singlemanifold for sampling a respective nutrient solution of each unit toprovide a sample of each nutrient solution, and a controller formeasuring at least one property, such as acidity, electricalconductivity or dissolved oxygen concentration, of each of the samplesand, in response to the measuring, and via the manifold, adjusting thecorresponding nutrient solution.

Preferably, the system also includes a mechanism for adjusting thetemperature of each nutrient solution. The controller is operative tomeasure the temperatures of the samples and, in response to themeasuring, and via the temperature adjusting mechanism, to adjust thetemperatures of the corresponding nutrient solutions.

A seventh aspect of the present invention is a device for providingadjustable shade. A basic such device includes a plurality of linearsupport members, such as the support wires of FIGS. 9A and 9B below. Thedevice also include, for each support member, a flexible tube thatsubstantially encloses that support member. The device also includes aninflation mechanism for reversibly inflating each tube.

Preferably, the tubes are opaque. Alternatively, the tubes aretransparent, and the device also includes a reservoir, of a colloidalsuspension of particles in a gas such as air, that is operativelyassociated with the inflation mechanism The colloidal particles are formodifying an optical property of the tubes.

Preferably, the device also includes, for each tube, a weight forholding the tube in a substantially straight vertical orientation whenthe tube is uninflated.

An eighth aspect of the present invention is a system and method forgrowing and harvesting plants. The plants are placed for growing in abed that includes a mechanism for moving the plants to a side of the bedwhen the plants are ready for harvesting. When the plants are ready forharvesting, the mechanism moves the plants to that side of the bed,where a mechanical harvester is used to harvest the plants. That theharvester is “mechanical”, here and in the first and ninth aspects ofthe present invention, excludes from the scope of the related attachedclaims a person who stands at the side of the bed and harvests theplants.

A ninth aspect of the present invention is a nutrient film techniquesystem and method for growing a plurality of plants. A basic system ofthe eight aspect includes a plurality of substantially parallel troughsfor supporting a nutrient solution, an opaque flexible sheet that has aplurality of apertures for supporting the plants, and a roller forreversibly unrolling the flexible sheet parallel to the troughs. Theroller is positioned relative to the troughs so that when the flexiblesheet is unrolled the flexible sheet substantially covers at least aportion of the troughs, with each aperture above a respective trough andsufficiently close to the trough that the roots of a plant that issupported by that aperture are at least pertly immersed in the nutrientsolution.

Preferably, the troughs are corrugations of a substantially rigid sheetsuch as a polymer-coated metal sheet.

Preferably, the system also includes a harvester that is adapted to bepositioned adjacent to the roller. The harvester is for harvesting theplants that are supported by the apertures as the flexible sheet isrolled off of the troughs onto the roller.

In a basic method of the eighth aspect of the present invention, anutrient solution is placed in a plurality of substantially paralleltroughs. A flexible opaque sheet, that includes a plurality ofapertures, is spread above at least a portion of the troughs so thateach aperture is above a respective trough. Each plant is inserted in arespective trough so that the plant is supported by its aperture withits roots at least partly immersed in the nutrient solution.

Preferably, for harvesting, the sheet is withdrawn from above thetroughs in a direction substantially parallel to the troughs whilewithdrawing at least a portion of each plant from its aperture when theplant reaches an end of the trough in which the plant's roots have beenat least partly immersed in the nutrient solution.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIGS. 1A-1C illustrate a basic rotating field system of the presentinvention with two rows of trays;

FIGS. 2A-2L illustrate how trays are rotated within a rotating fieldsystem with six rows of trays to insert empty trays between plantedtrays as needed;

FIG. 2M shows that the six rows of FIGS. 2A-2L are six of the rows of aneight-bed water unit, with the other two rows being nursery rows;

FIGS. 3A-3D illustrate preferred embodiments of a tray of the precedingFIGS.;

FIG. 4 shows one preferred embodiment of a protrusion of FIG. 3A;

FIG. 5 shows a nutrient solution circulation system for the eight-bedwater unit of FIG. 2M;

FIGS. 6 and 7 illustrate hardware for nutrient solution temperatureregulation;

FIG. 8 illustrates a monitoring and control system of a multi-unitrotating field system;

FIGS. 9A and 9B illustrate an array of inflatable tubes for shading abed of a rotating field system;

FIG. 10 shows a harvesting machine that is usable with the rotatingfield system or with the nutrient film technique system; and

FIGS. 11 and 12 illustrates the nutrient film technique system of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of hydroponics according to the presentinvention may be better understood with reference to the drawings andthe accompanying description.

Rotating Field System

The motivation for the basic rotating field system of the presentinvention is to create a conveyor system and mechanism to automaticallyrotate trays that bear plants in a growing bed in order to enable,planting, spacing, inspecting, treating and harvesting at the end orends of the bed, thus eliminating the need for walkways between thebeds.

Referring now to the drawings, FIGS. 1A-1C illustrate the basiccomponents of a basic rotating field system 10 of the present invention.FIG. 1A is a perspective view of system 10. FIGS. 1B and 1C arecross-sectional views of system 10 along cut A-A. System 10 is arrangedso that trays 12 are rotated automatically, inside a water bed 14 (whichis an example of the “pool” recited in the appended claims) as trays 12float on a nutrient solution 16 in bed 14. The use of such flotationallows a reliable, low maintenance, cost efficient solution andeliminates the need for use of beatings, shafts, sliding mechanisms andother mechanical fixtures for causing linear motion of trays 12. Bed 14includes a separation barrier (not shown) that allows for two rows 18 oftrays 12, one row 18 on each side of the barrier. Two pneumatic pistons20 (Y-pistons) push respective rows 18 of trays 12 in oppositeY-directions. Prior to movement of a row 18 by Y-piston 20 of that row18, that row 18 includes a gap 22 where one tray 12 is missing. Thissituation is illustrated in FIG. 1B for the right-side row 18 of FIG.1A. As a row 18 is pushed by its Y-piston 20, the last tray 12, that isnearest to that Y-piston 20, is retained by a spring arm (not shown)that prevents that tray 12, and the rest of trays 12 in that row 18,from moving back as that Y-piston 20 retracts back, leaving a vacanttray-sized gap 24 adjacent to Y-piston 20, as illustrated in FIG. 1C.Two other pneumatic pistons 26 (X-Pistons) then push the first tray 12in each row 18 into the vacant gaps 24, causing that tray 12 to join theother row 18 of trays 12. And then the two Y-pistons 20 again push rows18 of trays 12 in the Y-direction, one row 18 in the opposite directionof the other row 18. Arrows 28 show the way trays 12 are thus rotatedwithin bed 14. This procedure is governed, controlled, timed andsynchronized by a controller (see FIG. 8) and can be started and stoppedby the operator by pushing a switch.

FIGS. 2A-2L illustrate an enhanced rotating field system 30 that usessystem 10 as its basic building block. The motivation for system 30 isto do the spacing of the plants automatically. Plants takessignificantly less growing area as they build their biomass in theiryoung growing stage, and thus need more growing area in their latergrowing stage. In order to utilize the growing area better, and increasethe yields per square meter, plants are spaced differently during stagesof their growth cycle.

While system 10 automatically rotates trays 12 that carry the plantswithin bed 14, trays 12 never leave the single bed 14 and are onlyrotated within bed 14. The spacing can only be done manually, at one ofthe ends of bed 14, during the rotation. System 30 automatically,preferably using the same pneumatic pistons 20 and 26, both rotatestrays 18 within a single bed as needed and moves trays 18 betweenneighboring beds in order to space the plants by inserting an empty tray18 from a neighboring bed in-between trays 18 whose plants need spacing.

FIGS. 2A-2L show a growing and harvesting cycle in six adjacent beds(each with its own single row 18 of trays 12) of a water unit 14 (whichalso is an example of the “pool” recited in the appended claims). Thebeds are labeled A-F from upper left to lower right. FIG. 2A shows bedsC and D fully occupied by trays 12 planted with immature plants. Trays12 of beds A, B, E and F are empty. Beds A, B, E and F are ready toreceive trays 12 from beds C and D and to space those trays 12 forfurther growth of the plants.

FIG. 2B shows the plants of bed C sufficiently mature to be moved tobeds A and B for further growth.

FIG. 2C shows a planted tray 12 being moved from bed C to bed B while anempty tray 12 is moved from bed B to bed A.

Between the situations illustrated in FIGS. 2C and 2D, an empty tray 12is moved from bed B to bed C and beds A and B are rotated, to put twoempty trays 12 behind the planted tray 12 in bed B.

FIG. 2D shows a second tray 12 being moved from bed C to bed B while anempty tray 12 is moved from bed B to bed C. Note the two empty trays 12in bed B between the two planted trays 12.

Between the situations illustrated in FIGS. 2D and 2E, again, an emptytray 12 is moved from bed B to bed C and beds A and B are rotated to puttwo empty trays 12 behind the second planted tray 12 in bed B.

FIG. 2E shows the situation after three planted trays 12 have been movedout of bed C. The first tray 12 that was moved out of bed C is beingmoved from bed B to bed A. The second and third trays 12 that were movedfrom bed C are in bed B. All three trays 12 that have been moved frombed C have been replaced in bed C by empty trays 12.

Between the situations illustrated in FIGS. 2E and 2F, one of the twoempty trays 12 that separated the first two planted trays 12 in bed Bhas been moved to bed C, leaving only one empty tray 12 to separate thefirst two planted trays 12 in bed A.

FIG. 2F shows the situation after four planted trays 12 have been movedout of bed C. The first tray 12 that was moved out of bed C has beenmoved to bed A. The second tray 12 that was moved out of bed C is beingmoved from bed B to bed A. The third and fourth trays 12 that were movedfrom bed C are in bed B. All four trays 12 that have been moved from bedC have been replaced in bed C by empty trays 12.

FIG. 2G shows the situation after all but one of the planted trays 12have been moved from bed C to beds A and B. Beds A and B are beingrotated to bring the fourth planted tray 12 from bed B to bed A.

FIG. 2H shows the situation after all eight planted trays 12 have beenmoved from bed C to beds A and B. Each of beds A and B has four plantedtrays 12 separated by single empty trays 12.

Meanwhile, as shown in FIG. 2I, similar operations have been performedon beds D, E and F. The empty trays 12 in beds C and D are ready toreceive new plants. FIG. 2J shows beds C and D after replanting.

FIG. 2K shows the situation after continued growth in all six beds. Theplants in beds A, B, E and F are ready for harvesting.

FIG. 2L shows the situation after the plants in beds A, B, E and F havebeen harvested. The plants in beds C and D have grown to the point ofbeing ready to be moved to beds A, B, E and F for further growth.

FIG. 2M shows that water unit 14 of FIGS. 2A-2L actually includes eightbeds, with the two leftmost beds being used as a nursery. FIG. 2M alsopresents a calculation of the expected yield of a greenhouse withfifteen such water units 14. FIG. 2M illustrates how the yield of agreenhouse of the present invention, per unit area, is increased byadapting the inter-plant spacing to the size of the plants, rather thanusing only the largest needed inter-plant spacing as is doneconventionally.

Trays 12 are made of a low-density polymer foam such as polystyrenefoam. Trays 12 serve the following functions:

1. Provide support for the plants

2. Provide flotation for the plants

3. Enable the plants to be moved within and among the beds by pistons 20and 26 as needed

FIGS. 3A-3D illustrate preferred embodiments of a tray 12. FIG. 3A is aperspective view of one preferred embodiment of a tray 12. FIG. 3B is atop view of a similar preferred embodiment of tray 12. These embodimentsare substantially parallelepipedal blocks of polystyrene foam withapertures 32, for holding plants, that extend from the top surface 34 ofthe block to the bottom surface (not shown) of the block. The long 38and short 40 lateral sides of the block meet at champfers 44. FIGS. 3Cand 3D are cross sectional views of two other preferred variants of atray 12, showing two kinds of apertures 32 that extend from the topsurfaces 34 of these trays 12 to the bottom surfaces 36 of these trays12. Apertures 32 of the variant of FIG. 3C support their plants by theleaves of the plants. Apertures 32 of the variant of FIG. 3D supportsthe plants by their stems.

Trays 12 float in the water-based nutrient solution 16 of the beds, withtheir long sides 38 parallel and adjacent. Absent lateral protrusions 42from long sides 38 (shown in FIG. 3A), the water would tend to formadhesive films on long sides 38 of trays 12 that would cause trays 12 tostick together and that would inhibit the tray rotation that isillustrated in FIGS. 2A-2L. Protrusions 42 space trays 12 apart,preferably ten centimeters apart, to prevent sticking. FIG. 4 shows onepreferred embodiment of such a protrusion 42: a rigid insert, fabricatedseparately from tray, for insertion in a slot 46 in long side 38. (FIG.4 also shows two apertures 32 occupied by respective plants 48.) Tominimize friction and adhesion, protrusion 42 is smooth and/or is madeof a low friction material such as Teflon™. Alternatively, trays 12 arefabricated with integral protrusions 42. Although integral protrusions42 are made of the same material as these trays 12, trays 12 withprotrusions 42 have much lower areas of mutual contact than trays 12with smooth sides 38 and so do not stick together appreciably.

The edges of trays 12 where lateral sides 38 and 40 meet are champferedbecause the motion of pistons 20 and 26 may deviate from exactrectilinear motion by up to about 5 degrees. Champfers 44 also help tokeep trays 12 from sticking together. The champfer angles a and b shownin FIG. 3B preferably are between 15□ and 25□.

Depending on how apertures 32 in trays 12 are shaped and sized, and onthe nature of the plants, the plants can be supported either from theirbottom or from their sides.

Hybrid Hydroponics

The hydroponic technology of the present invention is a hybrid of DeepWater Culture (DWC) and Nutrient Film Technique (NFT)

Deep Water Culture (DWC)—also referred to in the prior art as “floatingraft hydroponics”—uses deep water bed typically on the order of one footdeep, containing all the dissolved nutrients required for plant growth.This nutrient solution is re-circulated past the bare roots of theplants. This technique has high productions costs and has problems withroot disease due to lack of sufficient dissolved oxygen.

Nutrient Film Technique (NFT) is a hydroponics technique that uses afilm of a thin stream of water, containing all the dissolved nutrientsrequired for plant growth, that is re-circulated past the bare roots ofplants in a trough, gutter or gulley, also referred to in prior art as achannel. Plants roots grown in this system have the same temperature andtemperature changes as the ambient temperature. This situation isunnatural and unhealthy for the plant (the temperature of the soil thatsurrounds a naturally grown plant is much more stable than thetemperature of the air above the soil) and can lead to poor performancedepending on the variability of the ambient temperature.

The hydroponic system and technique of the present invention is a hybridof DWC and NFT that combines the all the benefits of DWC and NFT whileeliminating almost all the problems. The system of the present inventionuses water beds that are deep enough (4 to 20 cm; preferably 5-6 cm) toenable temperature regulation and stability of nutrient solution 16 butnot so deep as to prevent the supply of sufficient dissolved oxygen innutrient solution 16.

Nutrient solution 16 is circulated on a per-unit basis. The beds areoriented north-south (so the long direction of trays 12, the“X-direction” of FIG. 1A, is east-west and the “Y-direction” of FIG. 1Ais north-south) and nutrient solution 16 circulates one way (e.g. northto south) in odd-numbered beds and the other way (e.g. south to north)in even-numbered beds. The pumping system used is airlift pumping.Airlift pumping is used routinely in aquaculture but has not been usedheretofore in hydroponics. FIG. 5 illustrates the airlift pumping systemof the present invention.

FIG. 5 shows a nutrient solution circulation system 50 for two adjacentbeds of the eight-bed water unit of FIG. 2M. At the bases of thesouthern half of the western bed and at the bases of the northern halfof the eastern bed are respective inlet tables 52. At the bases of thesouthern half of the eastern bed and at the bases of the northern halfof western bed are respective outlet tables 54. Conventional airliftpumps 60 pump nutrient solution 16 to inlet tables 52 via inlet pipes56. Nutrient solution 16 returns to airlift pumps 60 from outlet tables54 via outlet pipes 58. The overall circulation of nutrient solution 16is east to west in the northern halves of the two beds, north to southwithin the western bed, west to east in the southern halves of the twobeds, and south to north within the eastern bed.

The airlift pumping must be performed at a sufficiently high flow rateto achieve at least 80% O₂ saturation of nutrient solution 16. Merelybubbling air through water does not achieve this degree of saturationbecause the high surface tension of the bubble surface inhibitsdissolution of the air in the water. It is believed that microturbulenceat the bases of trays 12, especially at the openings of apertures 32,causes bursting of the bubbles and consequent efficient solution ofoxygen in nutrient solution 16. The cross section of the flowingnutrient solution 16 is about 1 m wide (the width of a tray 12).times.5cm deep and the flow rate through this cross section is about 6 to 8cubic meters per hour.

FIGS. 6 and 7 illustrate some of the hardware that is used forregulating the temperature of the nutrient solution of a bed. FIG. 6shows a bed 14 whose nutrient solution 16 is heated by a hot waterradiator 62 that receives hot water via a hot water inlet 64. FIG. 7shows a cooling tower that is used to cool nutrient solution 16 of aunit. Air is blown upward past a downward spray of nutrient solution 16.Because nutrient solution 16 is corrosive, the inside surfaces of thetower that come in contact with nutrient solution 16 are coated with aliner made of a polymer such as polyethylene.

The dissolved oxygen content, the electrical conductivity and the pH ofnutrient solution 16 also are monitored and controlled, on a per unitbasis. A monitoring and control system 70 of a multi-unit system isillustrated in FIG. 8. A central controller and data logger 72 samplesnutrient solution 16 of each unit separately via a respective bypasspipe 74. Missing water and nutrients, and acid for adjusting pH, areinjected to the unit as needed. (In FIG. 8, “Alfa” and “Beta” areconcentrated nutrient solutions, and the “Air Bleeder” is used formonitoring and controlling dissolved oxygen content.) Controller 72 alsosynchronizes the movement of pistons 20 and 26.

Conventionally, each hydroponic water unit has been controlled by itsown controller. In the multi-unit system of the present invention, asillustrated in FIG. 8, the redundancy of having separate sensors,separate pumps and a separate controller for each unit is eliminated byproviding a central controller 72 and an associated manifold 76 fromwhich respective bypass pipes 74 branch out to the various units. Eachbypass pipe 74 is provided with a pump (pumps P1 through Pn in FIG. 8)that is controlled by central controller 72. To monitor the condition ofa unit, central controller 72 opens the valve 78 associated with thatunit to obtain a sample of the unit's nutrient solution 16.

Natural ambient lighting (sunlight) is used to grow the plants. Thesystem is housed in a transparent or semitransparent building such as agreenhouse or a screen house. Above beds 14 of each unit is an array 80of east-west oriented flexible inflatable tubes 82 that are illustratedin perspective view and in cross-section in FIGS. 9A and 9B. FIG. 9Ashows tubes 82 as fully inflated. FIG. 9B shows tubes 82 as deflated.Support wires 84 suspend tubes 82 above beds 14. Weight wires 86 pulldeflated tubes 82 vertically flat, as shown in FIG. 9B. Tubes 82 areinflated by air to the degree needed for thermal screening (e.g. atnight) and illumination control. Additional illumination control isobtained by using a colloidal suspension of particles such as smokeparticles in the air that is used to inflate the tubes. The higher thedensity of the colloidal particles, the lower the level of illumination.Colored particles are used to control the spectrum of the light thatilluminates the plants. For example, green light, that is not used inphotosynthesis and may contribute to excessive heating of thegreenhouse, may be filtered out.

Alternatively, a system of tilting shutters is used. The shutters areclosed at night and are opened in the daytime at a tilt that changeswith the angle at which the sun is shining.

Planting and harvesting are done either manually or automatically. Onemethod of automatic planting and harvesting is robotic, as described inU.S. Pat. No. 6,508,033, which patent is incorporated by reference forall purposes as if fully set forth herein. Another method of automaticharvesting is as follows:

FIG. 10 shows a harvesting machine 90 that is usable with the rotatingfield system and method described above or with an automated NFT bedsystem as described below to automatically harvest leafy vegetables andother plants to be packed in bulk. Machine 90 has a set of knives 92 anda set of transport mechanisms which extend on a transverse frame. Theframe is mountable on or near the rotating field system units or nearthe automated NFT bed system. The rotating field system or the automatedNFT bed system is used to bring the harvested crop to machine 90 forharvesting. Knives 92 are operated by an electric motor. An electric airblower 96 and a conveyer can be the transport mechanisms used to movethe cut leaves or plants into a collecting container 94.

Harvesting machine 90 is displaceable on or near a hydroponics growingbed 14. Harvesting machine 90 includes a frame, having workingmechanisms and a structure supporting the working mechanisms. The framefurther has a set of mounts and a set of placement calibratingmechanisms extending at least approximately parallel to the growing bedplane, permitting a modification of the vertical position of the frame;a set of knives 92 powered by an electric motor for cutting the crop;connected to the structure by means that allow a modification of thevertical position of knives 92, two spaced apart first wheels extendingwhen considering the working direction behind the working tools allowinga modification of the vertical position of the first wheels in relationto the body, the first wheels being in contact with the ground or thesides of the bed or a rail set on the ground or connected to the bedduring working in order to support the body during working.

Plants that can be grown in the system of the present invention include:lettuce cos romaine, lettuce iceberg, lettuce lollorosa, lettucebutterhead, lettuce (curly leaf vars.), Chinese leaves (Chinesecabbage), chives, arugula, rocket, spring onions, pac-choy, mint leaves,dill, coriander, sweet basil, opal basil, rosemary, sage, tarragon,parsley (curly), parsley (flat), lemon grass and spinach.

Improved NFT Bed System

Most conventional NFT systems use individually fabricated troughs orgutters, usually formed from extruded plastic, and tilted at an angle of3□ to 5□ to allow the nutrient solution to flow past plants that areplanted in a growth medium such as peat moss within the gutters.

The NFT system of the current invention makes use of a corrugated metalsheet to create gutter-shaped troughs in a more cost-efficient way. Thesheet is coated with a polymeric material to prevent corrosion by thenutrient solution.

FIG. 11 shows an NFT system of the present invention: a gently (3□ to 5□tilted), polymer-coated corrugated metal sheet 102 above which is rolledout an opaque plastic sheet 106 with apertures 108. That sheet 106 isopaque prevents light from striking the water-nutrient film in thetroughs 104 of sheet 106 and promoting the growth of algae. Plants 110are planted in/through apertures 108.

FIG. 12 shows that sheet 106 is rolled out from a roller 112. Forharvesting, sheet 106 is rolled back onto roller 112 and plants 110 areharvested as they approach roller 112. Then sheet 106 is rolled back outand replanted.

Rolling out sheet 106 for planting and rolling sheet 106 back forharvesting allows the workers to stand at or behind the roller to do theplanting and the harvesting. With no need for aisles for the workers towalk along past sheet 106, the NFT system of the present inventioneconomizes on both the cost of labor and the cost of real estate.

FIG. 12 shows sheet 106 rolled out from the bottom of roller 112. In analternative configuration, sheet 106 is rolled out from the top ofroller 112. In this alternative configuration, harvesting machine 90 canbe moved up to the side of roller 112 opposite sheet 102, to harvestplants 110 as plants 110 come in over the top of roller 112.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.Therefore, the claimed invention as recited in the claims that follow isnot limited to the embodiments described herein.

1. A system for growing a plurality of plants, comprising: (a) aplurality of substantially parallel troughs for supporting a nutrientsolution; (b) an opaque flexible sheet having a plurality of aperturestherein for supporting the plants; and (c) a roller for reversiblyunrolling said flexible sheet parallel to said troughs and positionedrelative to said troughs so that when said flexible sheet is unrolledsaid flexible sheet substantially covers at least a portion of saidplurality of troughs, with each said aperture above a respective saidtrough and sufficiently close to said trough that roots of a plant thatis supported by said each aperture are at least partly immersed in saidnutrient solution.
 2. The system of claim 1, wherein said plurality oftroughs are corrugations of a substantially rigid sheet.
 3. The systemof claim 2, wherein said substantially rigid sheet is a polymer-coatedmetal sheet
 4. The system of claim 1, additionally comprising: (d) amechanical harvester, adapted to be positioned adjacent to said roller,for harvesting the plants that are supported by said apertures as saidflexible sheet is rolled onto said roller.
 5. A system for growing aplurality of plants, comprising: at least one trough for supporting anutrient solution, the at least one trough including a plurality ofchannels for supporting the nutrient solution; and, for each at leastone trough: a) an opaque flexible sheet having a plurality of aperturestherein for supporting the plants; and, a roller for reversiblyunrolling the opaque flexible sheet parallel to the at least one troughand positioned relative to the at least one trough so that when theopaque flexible sheet is unrolled the opaque flexible sheetsubstantially covers at least a portion of the at least one trough, witheach of the apertures above the at least one trough and sufficientlyclose to the at least one trough, such that roots of the plants extendthrough each of the apertures to be at least partly immersed in thenutrient solution.
 6. The system of claim 5, wherein the at least onetrough includes a corrugated sheet including a plurality of corrugationswhich define the plurality of channels of the at least one trough. 7.The system of claim 6, wherein the corrugations are of a depth to enabletemperature regulation and stability of the nutrient solution.
 8. Thesystem of claim 7, wherein the depth is approximately 4 cm toapproximately 20 cm.
 9. The system of claim 8, wherein the depth isapproximately 5 cm to approximately 6 cm.
 10. The system of claim 6,wherein the at least one trough is inclined.
 11. The system of claim 10,wherein the at least one trough is inclined at approximately 3 toapproximately 5 degrees with respect to the horizontal.
 12. The systemof claim 11, wherein the at least one trough includes a plurality oftroughs.
 13. The system of claim 12, wherein the plurality of troughsare arranged substantially parallel to each other.
 14. A method ofgrowing a plurality of plants, comprising the steps of: (a) placing anutrient solution in a plurality of substantially parallel troughs; (b)spreading a flexible opaque sheet, that includes a plurality ofapertures for supporting the plants, above at least a portion of saidtroughs so that each said aperture is above a respective said trough;and (c) inserting each of the plants in a respective one of saidapertures so that said one plant is supported by said respectiveaperture with roots of said one plant at least partly immersed in saidnutrient solution.
 15. The method of claim 14, additionally comprisingthe step of: (d) withdrawing said sheet from above said troughs in adirection substantially parallel to said troughs while withdrawing atleast a portion of each plant from said respective aperture thereof whensaid each plant reaches an end of said trough wherein said roots of saidplant have been at least partly immersed in said nutrient solution.